Bronze whaler description

Named for its bronze, or sometimes greyish-bronze upperside, this is a large, fairly slender shark with a moderately long and slightly pointed snout. The underside is white, and most of the fins have inconspicuous darker edges and dusky to black tips. Both the large, pointed first dorsal fin and the long pectoral fins are sickle-shaped. Often, a prominent white band runs down the flanks (3). Its common name ‘whaler’ arose in the nineteenth century, due to their habit of congregating around the carcasses of harpooned whales hanging along the side of whaling boats (4).

Related species

Bronze whaler biology

Despite the bronze whaler being a fairly common species, its biology is relatively poorly known due to confusion with other species (3). It is a viviparous shark, and thus the embryos develop within the mother and are provided nutrition via a yolk-sac placenta. Gestation is thought to last for about one year, after which a litter of 13 to 24 pups, measuring 59 to 70 centimetres, are born. Male bronze whalers reach maturity at around 13 years; females are mature at around 20 years (5).

Schools of adult and juvenile bronze whalers appear to segregate. Juveniles are present in shallow water all year round, whilst adults are found inshore only in spring and summer. Adult males occur in subtropical regions throughout the year, whereas females and immature sharks migrate to these regions during winter, and then return to temperate regions (and inshore) in the spring to breed (1). However, despite this migration, there is very little movement between adjacent regional populations (5). Nursery areas tend to be large and ill defined but include shallow banks, large shallow bays, inlets and harbours as well as the open coast (1).

Bronze whalers can be found singly, or in loose schools of up to one hundred individuals (1). They feed on bony fishes, such as sardines, mullets, hake and soles, as well as other prey such as sawfish, squid and cuttlefish (3)(5). Large numbers follow the winter sardine run off the southern Natal coast, South Africa to feast on one of their preferred prey (5). This powerful and fast shark is considered to be a dangerous species, and there have been a few provoked and unprovoked attacks on swimmers and divers (3).

Bronze whaler range

Occurs in most warm temperate waters in the Indo-Pacific, Atlantic and Mediterranean (5). The East Asia subpopulation has been recorded from the coastal waters off Japan, China, North and South Korea and southern Siberia (1).

Bronze whaler status

Bronze whaler threats

There is little information regarding the extent to which the bronze whaler is utilized, but it is undoubtedly caught for food, by sports anglers and taken as by-catch in a number of areas (1)(3)(5). As the bronze whaler is exceptionally slow to reproduce, it is particularly vulnerable to over fishing (3)(5). The East Asia subpopulation is the target of commercial fishing in China and contributes to the catch of shark fisheries in East Asia since the 1950s. However, fisheries for large coastal sharks in the region appear to have ceased during the 1970s due to declining catches. This apparent collapse of coastal shark fisheries indicates a decline in the East Asia subpopulation, and multi-species fisheries in the region are likely to continue to impact the population (1). The bronze whaler may also be threatened by degradation of their inshore nursery habitats, which are vulnerable to the effects of human development and pollution (1)(5).

Bronze whaler conservation

There are few conservation measures in place aimed specifically at the bronze whaler. In Australia and New Zealand, measures aimed at other species are likely to also be beneficial to the bronze whaler, for example, bans on taking school and gummy sharks from nursery areas in Tasmania, and a ban on gill netting out to five nautical miles from shore off the northwest North Island, New Zealand (1). Specific conservation actions may be required to conserve this magnificent ocean predator.

References

Randall, J.E., Allen, G.R. and Steene, R.C. (1990) Fishes of the Great Barrier Reef and Coral Sea. University of Hawaii Press, Honolulu, Hawaii.

Compagno, L.J.V. (1984) FAO Species Catalogue. Vol 4: Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Part 2: Carcharhiniformes. Food and Agriculture Organization of the United Nations, Rome.

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